Sash windows have been used for many centuries to beautify the exterior of many a home. The traditional sash window consists of two wooden panels, inset with glass panes. The wooden panels are set into their frames and can move in a horizontal or vertical direction to open and close the window. Weights and springs are set into the frame and are called a Yorkshire light, making the operating of the window easier. The earliest known example of a sash window can be viewed in the Vermeer painting, dating back to 1658, called The Milk Maid.